by Marc Basiliere
February 10, 2014
Not just for prototypes anymore…
Renishaw, the UK’s only manufacturer of additive manufacturing machines capable of building metal parts, has paired with Empire Cycles to build what is being called the world’s first 3D-printed metal bike frame. Laser melting, which is one of a group of technologies colloquially referred to as 3D printing, uses a laser to transform fine particles of metal and a CAD file into functional three-dimensional parts. In the case of the titanium alloys used for the Empire/Renishaw project, the process yields metal densities of 99.7%- denser and less pourous than can be achieved through casting of the same metal.
The long-ish video above illustrates the technique: a thin layer of titanium alloy powder is spread across a build platform and a thin cross-section of the part is fused by laser. Once complete, the platform drops and another thin layer of powder is spread and fused. Repeated hundreds of times, the result is a solid, three-dimensional part sitting in a bed of powdered metal, waiting to be excavated archeologist-style. To ensure part stability, Renishaw’s software designs and inserts removable supports, which are removed when parts are complete. The parts’ finish is currently on the rough side, typically requiring conventional machining for threads or other critical surfaces.
In addition to creating very dense parts, additive manufacturing frees designers and engineers from many of the geometric constraints associated with traditional casting or machining. This allows the part to more accurately reflect its structural requirements- or the designer’s aesthetic. Empire Cycles used Altair’s solidThinking Inspire software in the redesign of their seat tower to determine where material was needed- and where it could be removed. The resulting part – replacing a cast aluminum piece – is 44% lighter than its predecessor while retaining all required strength and stiffness. Complexity is not reflected in the build time, which frees designers to incorporate all sorts of features that might have otherwise required multiple pieces.
Originally committed only to seat mast optimisation and construction, given that project’s success Renishaw opted to work with Empire on an entire front end. The frame was broken into segments so as to be manufacturable within the AM250 laser melting machine’s 300mm maximum part build height. (Parts were subsequently assembled using Mouldlife adhesives.) Taken together, the switch in material and manufacturing techniques drop the weight of an Empire MX-6 Evo full suspension frame by a third: from 2,100g (4.6lb) to a competitive 1,400g (3.1lb). All figures are for the project’s first generation: Renishaw believe that, with additional analysis and optimisation, that weights could be reduced further without negatively impacting function or durability.
While not currently economical at commercial volumes, additive manufacturing does offer companies the ability to produce one-off or limited-production projects without costly tooling investment or excessive machining time. The process allows for relatively fast iteration and design development as well. As the cost of parts is related to the material consumed and machine time used, lightweight components are actually cheaper to build than heavier ones.